The communications industry is rapidly changing to adjust to emerging technologies and ever increasing customer demand. This customer demand for new applications and increased performance of existing applications is driving communications network and system providers to employ networks and systems having greater speed and capacity (e.g., greater bandwidth). In trying to achieve these goals, a common approach taken by many communications providers is to use packet switching technology.
Bridges, operating at the data link layer (layer 2), are generally used for connecting multiple local access networks (LANs). Bridges use source and destination Medium Access Control (MAC) address information to determine where to forward packets. In operation, a bridge maintains a data structure mapping MAC addresses to ports of the bridge. When the bridge receives a packet, the bridge inspects the destination MAC address and determines from the mapping data structure from which port to forward the packet. If the destination MAC address is not in the mapping data structure, the bridge broadcasts (or “floods”) the packet out each port. When a reply is received from the destination node, the bridge updates the mapping data structure associating the packet's source MAC address with the port on which the packet was received (as this is the port to forward packets destined for that MAC address). After this mapping is established, future packets with a destination address of that MAC address are not broadcast to every port, but to its mapped port.